Dielectric containing barium metatitanate



United States Patent DIELECTRIC CONTAINING BARIUM METATITAN ATE Werner Soyck, l1 Holzgartenstrasse, and Josef Herglotz, 14 Am Steg, both of Lauf, Pegnitz, Germany No Drawing. Filed Feb. 21, 1957, Ser. No. 641,471

19 Claims. (Cl. 10639) Patented Oct. 11, 1960 Example 2. The calculation of the composition is as follows: 65.7% BaO and 34.3% TiO corresponds to 71% BaCO and 29% Ti in the known material. To 87.4 parts of this mixture of BaCO and TiO are added 5 parts of clay and 7.6 parts of BaCO the latter being in an amount stoichiometrically equivalent to the silica in the clay. The percentage by weight of the BaCO clay, and H0 are then calculated in a known manner to give the composition shown in Example 2. In using a greater amount, i.e. clay double the amount BaCO has to be added. This results in the batch having the composition shown in the Example 3 in which there is chosen kaolin instead of clay, the calculations being the same as those set forth above, except that the amount of plasticizer is increased to 10% by weight of dry batch.

The following Examples 2 and 3 show batches accord ing to the invention. Example 1 is a normal metatitanate agents such as bentonite and kaolin. An addition of clay Y and kaolin had hitherto to be avoided because the silicic acid in this substance reacted in an unpredictable manner with the barium oxide so that the compounds containing barium metatitanate could not be obtained in the desired composition or the desired physical properties of the dielectrics could not be obtained. The necessity for using synthetic plasticizing agents, however, impairs the possibilities of moulding the crude mass in a desirable way. Consequently products containing barium titanate could only be prepared on a technical scale in simple moulds. The preparation of the constructional designs necessary in high voltage technique in the field of covering rims with increased thickness (edge enlargements) is rendered considerably more diflicult by the use of synthetic plasticizing processes.

The present invention provides the possibility of avoiding the said difiiculties and drawbacks and does this by a method of working according to which the products containing barium metatitanate can be prepared while using clay and kaolin as binding agents according to normal ceramic working methods. A proportion of clay of at least 5% of the dry batch of the raw materials is necessary.

According to this invention the total proportion of barium oxide in the bath is such that the whole of the titanic acid of the batch is neutralized to barium metatitanate and the whole of the silicic acid of the clay' is neutralized to barium metasilicate, but the amount of barium oxide is not substantially in excess of that necessary to accomplish this neutralization. If the proportion of clay in the batch does not exceed 10% of the dry raw materials, the essential properties of the barium metatitanate are retained, although to a reduced extent.

.In the disclosure of the Us. Department of Commerce, National Bureau of Standards, Research Paper RP 1776, volume 38, March 1947, Properties of Barium-Strontium-Titanate Dielectrics, there is described on page 341 in the specimen with the mark BT a material-with the following composition: 65.7 BaO and 34.3% Ti0 maturing temperature 1385" C. for two hours, DK=1500, power factor=1/400 using 1000 kc./s. The applicant adds to the known material an amount of clay to provide 5% clay by weight of the dry batch and a corresponding amount of BaCO being able to bind the amount of silicic acid of the clay, i.e. to 5 parts clay (according to the theoretical composition 46.5% silicic acid and 39.5% A1 0 remainder H O) 7.63 parts BaCO This will result in a batch having the composition shown in the Without clay taken from the above-mentioned publication.

Example 1 Example 2 Example 3 71% of B200; 702% of BaCO; 69% of BaCOa 29% of TiOz 24.8% of TiO; 21% of T101 5% of kaolin 10% of kaolm DK 1,500 DK 1,100 DK 900 tan 100X1O- tau 30Xl0- tan 60X 10- The dielectric constants and the power factors are in respect of room temperature and 1M megacycle. The batches in these examples were sintered at 1385" C. maintaining this temperature for two hours. The constitution analyses of the foregoing products is as follows:

Example 1 2 3 BaliO; percent 100 87. 7 75. 4 BaSiO: do 9. 9 l9. 8 A1202--- do-- 2. 4 4. 8

Extensive experiments have shown that it is only the above-mentioned content of barium oxide that produces ceramically useful masses and yields products having approximately the properties of barium metatitanate. An excess of barium oxide leads to porous substances, while too small a proportion of barium oxide leads to substances with an extremely small temperature range for the sintering which are ceramically useless.

The method according to this invent-ion may also be used, in the same way as for barium metatitanate, for masses which form barium metatitanate in conjunction with other oxides or oxide compounds.

As oxide compounds there may be mentioned the metatitanates of strontium, calcium and magnesium, and also the orthotitanate of magnesium, as well as compounds of barium oxide, such as barium zirconate, barium stannate and the like.

It has been found that the following ranges of composition result in an excellent vitrified ceramic dielectric:

75.492.5% of barium metatitanate 19.8-6.1% of barium metasilicate 4.81.4% of aluminum oxide 63.2% of barium carbonate 22.7% of titanium dioxide 9.1% of barium stannate and 5.0% of clay I are obtained which as regards their physical properties approximate to those fired without clay. V

The barium oxide can be introduced into the mass as barium carbonate or in the form of other barium compounds.

In the US. Patent No. 2,402,515 there is disclosed in Table III the favorable effect ofv the presence of 20% or less of barium-, strontiumor calcium-stannate orrthe characteristics of barium titanates in the form of mixed dielectrics. Table III contains as Example 3 a material consisting of 100 parts of barium titanate with- 10 parts of barium stannate, maturing temperature 1340 C. to 1375 C., having a dielectric constant of 3580 and a power factor of 270.10 using 1000 kc./s. According to our invention this material composition can be treated with clay in the following manner:

Without Clay With Clay Percentage by Weight 55.6 parts BaCO; 55 6 33,003...- BaOO 22.7 parts 'IiOz 22.7 T102 TiO 9.1 parts BaSn03 9.1 BaSnOL BaSnO;

maturing temperature: parts of weight clay clay 1,340-C. to 1,375 O. 7.6 parts of weight B3003. maturing temperature:

1,340 O. to 1,375 C.

The dielectric constants and the power factors are in both cases approximately the same, ice. the clay content does not substantially lower said qualities. The material according to .the invention has a dielectric constant of about 2500 and a power factor of about 50. 10- measured at room temperature and l megacycle. The constitution analysis of the'fired product of our invention is:

77.4% or 100 parts BaTiO 10.7% or 13 parts BaSnO 9.6% or 8.25 parts BaSiO 3.0% or 1.98 parts A1 0 Further the US. Patent 2,443,211 discloses dielectrics from barium titanate with 27 to 35% .of strontium titanate and the U.S. Patent 2,402,5 l6 discloses in Table I dielec-' sisting of barium oxide and barium carbonate, the barium compound being present in the amount necessary to react with the whole of the calculated titanic acid in the batch to form barium metatitanate and the whole of the calculated silicic acid in the plasticizing agent to form barium metasilicate, but not substantially in excess of that amount necessary to accomplish these reactions, said plasticizing agent being used in an amount between 5% and 10% by weight of the dry batch.

2. A method as claimed in'claim 1 wherein the barium compound is barium oxide.

3. A method as claimed in claim 1 wherein the barium compound is barium carbonate. 1

4. A method as claimed in claim 1 wherein the batch also includes an alkaline earth stannate.

5. A method as claimed in claim 1 wherein the batch also includes an alkaline earth zirconate.

6. A method as claimed in claim 1 wherein the batch also includes an alkaline earth titanate other than barium.

7. A dielectric comprising a fired batch consisting essentially of titanium dioxide, 5% to 10% of a clay plasticizing agent selected from the group consisting of kaolin and bentonite, and an amount of a barium com- 7 consisting of kaolin and bentonite.

9. A dielectric comprising a fired batch composed of 69% of barium carbonate, 21% of titanium dioxide and 10% of kaolin.

10. A dielectric comprising a fired batch composed of 63.2% of barium carbonate, 22.7% of titanium dioxide,

9.1% of barium stannate and 5% of clay plasticizing agent selected from the group consisting of kaolin and bentonite.

11. A vitrified ceramic dielectric consisting of 75.4

i 92.5% by Weight of barium metatitanate, 19.86.1% by Weight of barium metasilicate, and 48-14% by weight of aluminium oxide, the calculated'silicic acid and the aluminum oxide being proportionately inserted into the raw mass as a clay selected from. the group consisting of All the dielectrics referred to in these disclosures having I a content of barium metatitanate can be treated and im proved with favorable effect by adding, according to the present invention, clay and BaCG for forming barium metasilicate.

In all of the foregoing formulations the percentages are by weight.

This application is a continuation-in-part of our application Serial No. 352,011, filed April 29, 1953, now abandoned.

We claim:

1. A method of producing a dielectric containing barium metatitanate which comprises firing a batch consisting essentially of:

(a) titanium dioxide a (b) a clay'plasticizing agent selected from the group consisting of kaolinand bentonite (c) a barium compound selected from the group conkaolin and bentonite.

12. A vitrified ceramic dielectric consisting of 75.4 92.5%.by weight of barium metatitanate, an alkaline earth titanate other than barium, l9.86.l% byweight of barium metasilicate, and 4.8-1.4% by weight of A1 0 the calculated silicic acid and the aluminum oxide being proportionately inserted into the raw mass as a clay se-. lected fromthe group consisting of kaolin and bentonite. 13. A vitrified ceramic dielectric consisting of 754- 92.5% by weight of barium metatitanate, an alkaline earth stannatc, 19.8-6.1% by weight of barium metasilicate, and 4.8-1.4% by weight of A1 0 the calculated silicic acid and the aluminumoxide being proportionately inserted into'the raw mass as a clay selected from the group consisting of kaolin and bentonite.

1-4. A vitrified ceramic dielectric consisting of 75.4- 92.5% by weight of barium metatitanate, an alkaline earth zirconate, l9.86.l% by weight of barium metasilicate, and 4.8l.4% by weight of aluminum oxide, the calculated silicic acid and the aluminum oxide being proportionately inserted into the raw mass as a clay selected from the group consisting of kaolin and bentonite; V i a V 15. A vitrified ceramic dielectric consisting of 75.4-

by weight of barium metasilicate, and 4.8-1.4% by weight of aluminum oxide, the calculated silicic acid and the aluminum oxide being proportionately inserted into the raw mass as a clay selected from the group consisting of kaolin and bentonite.

16. A method as claimed in claim 1 in which the plasticizing agent is kaolin.

17. A method as claimed in claim 1 in which the p1asticizing agent is bentonite.

18. A dielectric as claimed in claim 7 in which the plasticizing agent is kaolin.

19. A dielectric as claimed in claim 7 in which the plasticizing agent is bentonite.

References Cited in the file of this patent UNITED STATES PATENTS 2,098,812 Pulfrich Nov. 9, 1937 2,165,819 Albers-Schonberg July 11, 1939 2,402,515 Wainer June 18, 1946 6 2,402,516 Wainer June 18, 1946 2,424,111 Navias et a1. July 15, 1947 2,443,211 Wainer et al. June 15, 1948 2,452,532 Wainer Oct. 26, 1948 2,467,169 Wainer Apr. 12, 1949 2,486,560 Gray Nov. 1, 1949 2,691,597 Mollers Oct. 12, 1954 2,815,291 Rogatz Dec. 3, 1957 FOREIGN PATENTS 579,868 Great Britain Aug. 19, 1946 142,833 Australia 1951 OTHER REFERENCES Ries: Economic Geology, pub. 1925, by John Wiley & Sons, N.Y., chapter IV (pages 174-175).

Searle: Refractory Materials, pub. 1950, London, by Chas. Griflin & Co. (page 27). 

1. A METHOD OF PRODUCING A DIELECTRIC CONTAINING BARIUM METATITANATE WHICH COMPRISES FIRING A BATCH COMSISTING ESSENTIALLY OF: (A) TITANIUM DIOXIDE (B) A CLAY PLASTICIZING AGENT SELECTED FORM THE GROUP CONSISTING OF KAOLIN AND BENTONITE (C) A BARIUM COMPOUND SELECTED FROM THE GROUP CONSISTING OF BARIUM OXIDE AND BARIUM CARBONATE, THE BARIUM COMPOUND BEING PRESENT IN THE AMOUNT NECESSARY TO REACT WITH THE WHOLE OF THE CALCULATED TITANIC ACID IN THE BATCH TO FORM BARIUM METATITANATE AND THE WHOLE OF THE CALCULATED SILICIC ACID IN THE PLASTICIZING AGENT TO FORM BARIUM METASILICATE, BUT NOT SUBSTANTIALLY IN EXCESS OF THAT AMOUNT NECESSARY TO ACCMPLISH THESE RAACTIONS, SAID PLASTICIZING AGENT BEING USED IN AN AMOUNT BETWEEN 5% AND 10% BY WEIGHT OF THE DRY BATCH. 